The Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 2001-192938 discloses a spinning device that spins a yarn by opening a bundle of fibers using a whirling air current generated by a pneumatic spinning nozzle and twisting the fibers while winding them around the periphery of a tip portion of a hollow guide shaft. In this configuration, an air exhausting space is in communication with a hollow chamber in the tip portion of the hollow guide shaft. A whirling air current generated by the pneumatic spinning nozzle flows from the hollow chamber to the air exhausting space, where it is exhausted.
Then, the Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 2001-192938 points out the following problem. When the fibers are looped around the periphery of the hollow guide shaft in the air exhausting space, fibers subsequently discharged from the hollow chamber may be twined around the loop. In this case, the subsequent fibers may not be discharged to the exterior. This prevents air from flowing normally out of the hollow chamber, thus hindering the normal whirling current in the hollow chamber. This causes a defect in the yarn (what is called a weak yarn). The Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 2001-192938 further states that such a problem can be solved by increasing the outer peripheral length of lager diameter portion of the hollow guide shaft which is located in the air exhausting space, above the mean fiber length of the bundle of fibers.
However, even with the above increase in the outer peripheral length of the larger diameter portion, the fibers may be looped around the larger diameter portion. Accordingly, the above configuration is not always sufficiently effective in preventing the weak yarn.
In response to a recently growing demand for multi-type small-amount production, the same spinning device may be used to spin fibers of various fiber lengths. The shape of the hollow guide shaft may be set so as to increase the outer peripheral length above the possible maximum fiber length. However, this may increase the size of the spinning device.
A description has been given of the problems to be solved by the present invention. Now, a description will be given of means for solving the problems and their effects.